Impact of oil on natural regeneration of vegetation

The impact of oil spills on wetland and upland seed banks was assessed. Results showed that application of two litres of oil per sq.m. did not affect seedling emergence. Eight litres per sq.m. reduced emergence by 50 per cent, but sufficient number of seedlings have emerged to re-establish vegetation. Differences in species richness between communities and species were noted; they were attributed to traits which promote long-term dormancy and which may also provide resistance to oil. Intraspecific genetic variations declined for particular traits, but not for others, suggesting that persistence of recovering vegetation may be impacted if the affected trait is important to survival and reproduction. Spills occurring in wetlands may require little active restoration, however, little natural recovery may be expected in an oak-pine community. Different soil texture and composition may also affect germination after a spill by influencing binding ability and oxygen content. It was suggested that an alternative approach to restoring forest communities might be the addition of seed-containing soil to the oil spilled sites. The increase in seedling density is a factor affecting revegetation. 40 refs., 2 figs